#! /bin/bash

FIRSTEXPORT="first export"
READONLY="read only"

# export FIRSTEXPORT
export FIRSTEXPORT
# print all export variables
export -p

# set readonly variable
readonly READONLY
# print all readonly variable
readonly -p

# cancel varaible FIRSTEXPORT, use FIRSTEXPORT= only
# delete it's value, not the variable itself.
unset FIRSTEXPORT
echo $FIRSTEXPORT
echo $READONLY

cat > mv.txt <<"EOF"
this file has the pattern?
EOF
if grep has mv.txt > /dev/null
then
	echo "have pattern";
else
	echo "don't have pattern";
fi
rm mv.txt


